It sounds to me like you need some time alone to try to get more clear on how to handle your time with your kids. For everyone's sake. Then set that out to everyone...see how it goes? Since you only see your kids every other weekend, I personally believe its super important, even if you get married, to always have special private time alone with your kids, and even time with each individual child if possible. Perhaps you can work out a comprimise of a good dose of time with your kids....they deserve that, and then some fun time with your girlfriend where your all doing a activity everyone can enjoy. In the end, its up to you to decide what works for YOU, what you think is best for you and your kids...they come first...and go from there.
As far as parenting, I can wholeheartedly say that I know my daughter thrives off it when I set clear boundries and consequences and stick to them. Kids NEED boundries to be healthy...and I have never experienced her loving me less as a result of having boundries. I'm not saying I don't have to endure her tantrums, mean words sometimes, her angst...it tears me up inside...but when I stick to my word, she always gets over it...quicker than I usually think (I think it takes ME longer to recover frankly), and life goes back to whats next...
As far as parenting, I can wholeheartedly say that I know my daughter thrives off it when I set clear boundries and consequences and stick to them. Kids NEED boundries to be healthy...and I have never experienced her loving me less as a result of having boundries. I'm not saying I don't have to endure her tantrums, mean words sometimes, her angst...it tears me up inside...but when I stick to my word, she always gets over it...quicker than I usually think (I think it takes ME longer to recover frankly), and life goes back to whats next...